1983 Mercury 90hp to 115 hp

[PerKman]

I have a good running 1983 Mercury 90hp inline 6 motor and was wondering if I could revamp to 115hp. The reason I ask is that all specs for both 90 and 115 are identicle (i.e. bore, stroke, displacement, gear ratio, primary throttle pickup,etc). The only differences I find are:<br />#1- the secondary throttle pickup on the 90 is 1-3 degrees BTDC the 115 is 5-7 ATDC <br />#2- the full throttle rpm for the 90 is 4500-5000 the 115 is 5000-5500 and<br />#3- the main carburetor jet sizes differ .002 to .004 depending on elevation and the 115hp serial number. If this is feasable please explain the procedure(secondary pickup adjustment etc.)

 

[Mercury140-I6]

Re: 1983 Mercury 90hp to 115 hp

Also the port timming and port size are different, which would require tearing into the motor and having it machined and put back together. Easier and cheaper to just get a 115 powerhead and replace your 90 with the 115. I know, I did the same thing, but replaced a 115 with a 140 (Both 1979).<br /><br />Hope this helps.<br /><br /> http://www.myfishingpictures.com/showphoto.php?photo=13002&sort=7&thecat=500&password= <br /><br />Craig

 

[jimmbo]

Re: 1983 Mercury 90hp to 115 hp

Reed blocks, exhaust tuner, pistons, and a piece in the throttle linkage are different too.